Institute of Quality Standard and Monitoring Technology for Agro-products of Guangdong Academy of Agricultural Sciences, Guangzhou, 510640, PR China; Key Laboratory of Testing and Evaluation for Agro-product Safety and Quality, Ministry of Agriculture, Guangzhou, 510640, PR China.
Guangdong Agricultural Science Monitoring Technology Co., Ltd, Guangzhou, 510640, PR China.
Chemosphere. 2022 Sep;303(Pt 2):134663. doi: 10.1016/j.chemosphere.2022.134663. Epub 2022 Apr 18.
Low molybdenum (Mo) bioavailability in acidic soil obstructs vegetable nitrogen assimilation and thus increases the health risk of vegetable ingestion due to nitrate accumulation. Constantly providing available Mo in acidic soil is a challenge for decreasing nitrate accumulation in vegetables. In this study, three Mo application methods, including biochar-based Mo slow-release fertilizer (Mo-biochar), seed dressing, and basal application, were investigated to enhance Mo bioavailability in acidic soil and nitrogen assimilation in Chinese flowering cabbage (Brassica parachinensis). The results showed that Mo-biochar constantly and sufficiently supplied Mo nutrients throughout the growing period of Brassica parachinensis, as evidenced by the soil available Mo, plant Mo uptake, and Mo values. The improved Mo supply was attributed to the alleviation of acidic soil (pH from 5.10 to 6.99) and the slow release of Mo adsorbed on biochar. Mo-biochar increased the nitrate reductase (NR) activity by 238.6% and glutamate dehydrogenase activity by 27.5%, indicating an enhancement of the rate-limiting steps of nitrogen assimilation, especially for nitrate reduction and amino acid synthesis. The increase in Mo-containing NR could be directly ascribed to the high level of Mo in Brassica parachinensis. Compared with the control, the nitrate content of Brassica parachinensis decreased by 42.9% due to the nitrate reduction induced by increased NR. Additionally, Mo-biochar was beneficial to vegetable growth and quality. In contrast, the transformation from NO to NH was blocked with Mo seed dressing and basal application because of low Mo bioavailability in the soil, resulting in a high nitrate content in Brassica parachinensis. Conclusively, Mo-biochar can slowly release Mo and improve the neutral environment for Mo bioavailability, which is an effective strategy to mitigate the high nitrate accumulation of vegetables planted in acidic soil.
土壤酸化降低钼生物有效性，阻碍蔬菜对氮素的同化，从而增加硝酸盐积累对人体健康的威胁。在酸性土壤中持续提供有效钼是降低蔬菜硝酸盐积累的挑战。本研究采用 3 种施钼方式，包括生物炭基钼缓释肥（Mo-biochar）、拌种和基肥，以提高酸性土壤中钼的生物有效性和花椰菜（ Brassica parachinensis ）对氮素的同化。结果表明，Mo-biochar 持续且充分地为花椰菜提供钼营养，这表现在土壤有效钼、植株钼吸收和钼值上。Mo-biochar 提高了钼供应，这归因于它改善了酸性土壤（pH 值从 5.10 增加到 6.99）和对吸附在生物炭上的钼的缓慢释放。Mo-biochar 提高了硝酸还原酶（NR）活性 238.6%和谷氨酸脱氢酶活性 27.5%，表明氮同化的限速步骤得到了增强，尤其是硝酸盐还原和氨基酸合成。含钼 NR 的增加可直接归因于花椰菜中高水平的钼。与对照相比，Mo-biochar 处理降低了花椰菜硝酸盐含量 42.9%，这是由于 NR 增加诱导硝酸盐还原。此外，Mo-biochar 有利于蔬菜生长和品质。相比之下，Mo 拌种和基肥处理由于土壤中钼生物有效性低，抑制了 NO 向 NH 的转化，导致花椰菜硝酸盐含量升高。综上，Mo-biochar 可缓慢释放钼并改善钼生物有效性的中性环境，是减轻酸性土壤种植蔬菜硝酸盐积累的有效策略。
